The present invention relates to trackballs and more particularly to a trackball device with target ball having uniformly embedded particles for creating a clear image of an illuminated portion of the ball, resulting in a precise corresponding movement of cursor on a display of computer.
A conventional trackball device 1 such as disclosed in U.S. Pat. Nos. 5,288,993 and 5,703,356 is shown in FIG. 1 comprising an upper housing 10 and a lower housing 11 being for example threadedly secured together. Necessary circuitry and electronic components are mounted within trackball 1. One button (or more than one button in other implementations) 12 and a circular opening 14 are formed on upper housing 10. A ball 20 is fitted in the opening 14 with the upper half portion projected above the surface of upper housing 10 such that user may rotate ball 20 with hand. An optical device 30 is adjacent ball 20 within the trackball device 1 for emitting light to ball 20 and creating an image of an illuminated portion of the ball 20 from the reflected light thereof so as to process and calculate a direction and distance proportional to the rotation of the ball 20 as detailed below.
An enlarged and detailed view of ball 20 and optical device 30 is shown in FIG. 2. Optical device 30 comprises a light source 31 for flooding a portion of ball 20 with diffuse light and a photodetector 32 for creating image of an illuminated portion of the ball 20 from the reflected light thereof. Trackball device 1 then processes such fetched images and compares the difference between a previous image and a current one. Further, a direction and distance proportional to the rotation of the ball 20 is calculated if the difference exists. Hence, a corresponding movement of cursor will be shown on a display screen of for example personal computer which is electrically coupled to trackball device 1. In view of above, the quality of fetched image will be critical to the precision of the calculated direction and distance of a moving cursor.
A number of things are proposed herein for manufacturers and designers to consider. For example, the smoothness of the rotation and the maneuverability of ball 20 are important factors since trackball device 1 is designed to be rotated by user for moving a cursor on screen. Conventionally, ball is of hard construction (e.g., molded thermoplastic) and has a very smooth surface for facilitating rotational operation by reducing friction and for preventing from being deformed. But this is unsatisfactory for the purpose for which the invention is concerned because an intense diffuse light is reflected (since the surface of ball 20 is very smooth) after light is flooded onto the ball 20 from light source 31. As such, the effect of photodetector 32 of creating an image of an illuminated portion of the ball 20 from the reflected light is compromised while only the intense diffuse light is received. This makes a correct comparison between the previous image and the current one impossible. Thus a correct calculation of direction and distance proportional to the rotation of the ball 20 is not obtained. Hence, a precise movement of cursor will not be shown on display screen. The prior art shown in FIG. 2 discloses a technique of printing a plurality of uniformly arranged spots 21 on the surface of ball 20 for decreasing the reflectivity of diffuse light from ball 20. As a result, a clear image of an illuminated portion of the ball 20 may be created by photodetector 32. However, the previous design still suffered from several disadvantages. For example, it is high in manufacturing cost. Further, the sharpness of the created image is necessarily limited by the smoothness of the surface of ball 20.
Thus, it is desirable to provide an improved trackball device in order to overcome the above drawbacks of prior art.
It is an object of the present invention to provide a trackball device wherein the ball is formed of transparent or semitransparent hard thermoplastic material having the advantages of very smooth surface, being resistant to deform, reduced friction, and high maneuverability.
It is another object of the present invention to provide a trackball device wherein a plurality of uniformly disposed reflective particles are formed within the transparent or semitransparent hard thermoplastic material such that most of emitted diffuse light from a light source is penetrated through the ball and a portion of the penetrated light is reflected to a photodetector through the surface of ball by the particles. Photodetector can create an image of an illuminated portion of the ball from the reflected light thereof and calculate a correct direction and distance proportional to the rotation of the ball. Hence, a precise corresponding movement of cursor will be shown on a display screen. As a result, the prior art drawback of inconsistency between the rotating ball and the moving cursor is eliminated.
The above and other objects, features and advantages of the present invention will become apparent from the following detailed description taken with the accompanying drawings.